Self-aligning vertical shaft



Aug. 5, 1952 N, SVENSJO 2,606,082

SELF-ALIGNING VERTICAL SHAFT Filed NOV. 10, 1947 Ti l.

INVENTOR.

NI LS. EDVIN SVENSJO ATTORNEY Patented Aug. 5, 1952 UNITED STATES 2,606,082 SELF-ALIGNING VERTICAL SHAFT Nils Edvin Svensjo, Nockeby,

Aktiebolaget Separator, "Stockholm,

a corporation of Sweden Application November 10, 1947, Serial No. 7 85,035 In Sweden November 11, 1946 This invention relates to centrifuges and more particularly to an improved top bearing for the spindle of a centrifugal bowl.

High speed centrifuges are generally provided with a radially elastic top bearing, which prevents the vibrations of the bowl spindle from being transmitted to the frame of the centrifuge. In this way a smooth and easy operation of the centrifuge is obtained. The vibrations of the spindle are due to some unbalance remaining in the bowl after it has been balanced. The springing and dampening of the top bearing are such that even the lateral deviations of the spindle when it is passing the most critical speed, are entirely absorbed by the spring system of the bearing. The ability of absorbing vibrations is due not only to the elasticity of the spring system of the bearing but also to the dampening which is caused by the friction between the different parts of the spring system or by the interior friction of a rubber ring, or the like, serving as the elastic element. The ordinarily existing dampening factor is quite sufiicient for the absorbing of all radial movements due to normal unbalance of the bowl.

Under certain circumstances, however, the bowl may acquire a greater unbalance than usual. The radial movements of the spindle will then have greater energy than is normally the case, and the dampening effect of the top bearing is not sufficient to absorb and dissipate the whole amount of energy, with the result that the solid parts of the top hearing will collide and very strong vibrations will be transmitted to the centrifuge frame, involving risks of deformation or breaking of important parts of the centrifuge.

The unusually large deviations of the spindle can, of course, be counteracted and the energy of the radial movements absorbed by a materially increased dampening of the top bearing. Tests along this line have been made but have not given satisfactory results. A top bearing of this kind has proved to transmit the normally occurring vibrations to the frame in such a way that the running has been stiff. As a matter of fact, a top bearing with strong dampening will, if special precautions are not taken, be a stiff top bearing, that is, its elastic qualtities will approach those of a rigid bearing. This stiffness of the top bearing involves, in addition to the stiff running, a considerably increased wearing, because the forces developed in the bearing will be considerably larger than normally. In addition,

,the forces transmitted to the frame are a drawback. An adequate increase of the dampening 3 Claims. (Cl. 308-143) Sweden, assignor to Sweden,

at the bearing has therefore not proved to be an acceptable way of solving this problem.

One object of the present invention resides in the provision of a top bearing assembly for centrifugal bowls, which overcomes the above-noted difficulties.

Another object is to provide an improved top bearing assembly of simple and a compact construction which, by a radial spring action, absorbs the vibrations of the bowl spindle so as to prevent their transmission to the centrifuge frame, the assembly being of a unitary character whereby it can readily be installed or removed.

According to the preferred form of the invention, the bearing assembly includes a dampening system which is effective at all times to absorb the spindle vibrations, and a second and stronger dampening system cooperating with the first one but which does not function until the deviations of the spindle (the radial movements) have exceeded a certain normal amount. Thus, there is a certain margin within which the spindle and the parts which accompany it in its radial movements can move under normal conditions, so that the running of the centrifuge is smooth and easy and the forces transmitted to the frame are extremely small. Not until this margin has been exceeded does the more powerfully functioning dampening device come into action. Comparatively large forces are thereby transmitted to the 1 frame but this can be allowed because the large unbalance occurs only occasionally, generally due Mom or more of the nozzles in the outer wall of the bowl being clogged, causing the sludge to deposit on one side of the bowl. Furthermore, the abnormally large radial movements occur only when a critical speed is being passed. At normal running of the centrifuge the stronger dampening system does not cause any inconvenience because it does not function at all.

The dampening device can, with consideration to the foregoing conditions, be constructed in different ways. It has previously been attempted to increase the dampening by providing the radially movable part of the top bearing with a plane flange pressed between a plane fixed surface and a plane ring influenced by a spring. By this arrangement, an efficient retardation of the radial movements has been obtained but with a drawback that the position of the movable flange is not fixed. and it may disturb the running of the centrifuge in normal use because the radially movable part of the top bearing hits the movable flange if this occasionally has an eccentric position. The flange is maintained with comparatively large force in this position between the spring-actuated ring and the plane fixed surface. What is lacking in such an arrangement is an ability of the flange to return to normal position after moving sideways at strong deviations.

For a better understanding of the invention, reference may be had to the accompanying drawing, in which Fig. l is a vertical sectional view of one form of the new bearing assembly; 1

and Fig. 2 is a similar view of another form of the assembly. 7

The bowl spindle I rotates in the usual way in the frame F of the centrifuge. The upperpart of the spindle is surrounded and engaged by a bearingi having a rotating inner race 2 and a non-rotating'outer' raceZ The outer race Z fits closely in-a 'non-rotatingring 3 which is movable radially with the bearing'and the spindle. A plurality of plungers, one of which is sho-wn'at 4, are spaced around the outside of ring'3 and are slidable radially in a stationary member'fi. The plungers 4, of which there are at leastthree, are evenly spaced around the ring 3 and engage its outer wall. Each plunger is urged inwardly against the ring by 'a'coiled'spring 4 seated against a cap 4 threaded in thecstationary member 5.

A pin-6 projects from each-plunger through the corresponding cap, the outer ends of the pins being normally'spaced from :a double-conical ring 1 to provide-a clearance 8. The ring I is pressed between two conical rings Sand I which are pressed toward each other, as by means of vertical compression springs II acting upon the ring ID.

The ring 3 is supported by-a top flange 3 resting upon the stationary member 5 and slidable radially thereon. The member -5, in turn, rests upon the frame part F towhich it is removahly secured by-bolts G. A cover-H is secured to the member-5 by bolts J and serves to oppose the upward pressure of springs I I against the-rings 7, Sand 1%, the springs being seated in the member 5. In this way, the entirefbearing assembly can-be removed as a unit from the frame by simply detaching the cover-H and the overlying flanged-member K on the spindle; and unscrewing the bolts G.

The-device functions in the following way: As long as the radial movements of the spindle'and the movable bearing part 3 are kept within the: limit which isdetermined by the clearance space 8, the rotation goes on under normal conditions. Not until the deviations become larger do the pins 6 contact the ring 1 and press this sideways.

The ring "I allows additional movement sideways but acts strongly ;to retard such additional movement, whereby-the radial movements of the spindle and the bearing parts are strongly dampened. The conicity of the rings I, 9, I0 is suitably chosen-so that the ring I is moved back to normal =position as shown, by the forces of the springs I I. Thus, the ring "I is prevented from remaining in" any eccentric position and disturbing theoperation of the centrifugeat normal unbalance.

The rings 1, 9, I0 should be made of such ma.- terial that there is no danger of seizing of the gliding surfaces during normal running. -In

order to obtain sufficient strength of the material for this purpose, suitable metals and metal alloys may be used. One of the friction parts can be made of the kind of porous metal or metal alloy which is used for self-lubricating bushings. As indicated in Fig. 1, the rings 9 and II] can be provided with inserts in the form of rings or blocks I2 and I3 made of some suitable brakematerial, e. g., such as is used in brake bands or friction clutches. The parts I2 and I3 can, of course, be inserted in the ring 1 instead of the ringse, #8. It is also possible to use solid metal against the same metal, provided that there is f satisfactory lubrication of the friction surfaces.

'In the embodiment of the invention shown in Fig. 2 the stronger dampening element is a rubber-ring I4 placed on a metal ring I 5 fixed to the member 5 on the frame F. The rubber ring I4 is covered with a metal ring I6 and encircled by a cylindrical flange I8 connected to the radially movable part I'I. Ther is a clearance space 8 between'the parts I'6and'I8 of the same size and. with the same function as'the clearance space 8 in'Fig-l. The purpose of the metal ring I 6 is to secure a predetermined and unchangeable diameter ofthedampening element which comprises the'rubber ring M. This arrangement functions substantially in the same way as the arrange-. ment shown in Fig. 1. The spindle and the 'adially'movable part I l of the top bearing move within a certain limit entirely independently of the dampening device'inclu'ding the rubber ring I i, these movements being opposed by the springs i Notuntil abnormal deviations'occur do the parts It and=I Bengage and cause a strong dampening of the'raldial movements.

The movable part of theball bearing housing does not, of course, move at right. angles to the ring 1 (or the ring I 4) which serves as the dampening element, but undergoes more or less a circulating-movement. When the deviations become so large thatcontact occurs between the pins 6 and thei ing I (or between the parts It and I8), theparts will therefore slide against each other. This causes a further dampening of the radial -motion component of the top bearing part. This dampening can'suitably'be strengthened by treating the ccntactsurfaces in such a way that the CGBffiGiBl'ltOffliCtiOll is increased. One or both parts can be covered with some friction material, such as is used for brakes, clutches and the like. In thisway, an increased dampening and braking of the abnormally large radial movements is obtained. It-may-alsobe desirable to provide the contact surfaceswith some sound-absorbing material so that shocks between these surfaces will not cause disturbing sounds.

Iclaim:

1. [In a centrifuge having-a spindle and a frame supporting the spindle for rotation, a top bearing assembly for the spindle comprising'a bearing surrounding the samegmeans for'securing the bearing in a-fixed axial position relative to the spindle, a spring dampeningdevice surrounding the bearingandacting to oppose radial deviations thereof due to normal vibrations of the spindle, said device being yieldable radially incident to said deviations'and having an annular surface surrounding the bearing and forming an axial path along which the spindle and bearing are slidable vertically relativeto said device, a frictional dampening device normally inoperative upon said'bearing butadaptedto frictionally opposeabnormal vibrations of the spindle, said frictional damping "device including means for. automatically returning said device to a predetermined normal position upon resumption of said normal vibrations, and means for operatively connecting said frictional dampening device with the bearing only when said radial deviations exceed a predetermined amount, said frictional dampening device including an elastic ring concentric with the spindle axis and upon which said connecting means are operable to compress the ring radially, the ring having a high resistance to radial compression.

2. In a centrifuge having a spindle and a frame supporting the spindle for rotation, a top bearing assembly for the spindle comprising a bearing surrounding the same, means for securing the bearing in a fixed axial position relative to the spindle, a spring dampening device surrounding the bearing and acting to oppose radial deviations thereof due to normal vibrations of the spindle, said device being yieldable radially incident to said deviations and having an annular surface surrounding the bearing and forming an axial path along which the spindle and bearing are slidable vertically relative to said device, 'a frictional dampening device normally inoperative upon said bearing but adapted to frictionally oppose abnormal vibrations of the spindle, said frictional damping device including means for automatically returning said device to a predetermined normal position upon resumption of said normal vibrations, and means for operatively connecting said frictional dampening device with the bearing only when said radial deviations exceed a predetermined amount, said frictional dampening device including an elastic ring concentric with the spindle axis, and a metal ring covering the elastic ring, said connecting means including a flange movable radially with the bearing and normally spaced from but engageable with the metal ring.

3. In a centrifuge having a spindle and a frame supporting the spindle for rotation, a top bearing assembly for the spindle comprising a bearing surrounding the same, means for securing the bearing in a fixed axial position relative to the spindle, a, sprin dampening device surrounding the bearing and acting to oppose radial deviations thereof due to normal vibrations of the spindle, said device being yieldable radially incident to said deviations and having an annular surface surrounding the bearing and forming an axial path along which the spindle and bearing are slidable vertically relative to said device, a frictional dampening device normally inoperative upon said hearing but adapted to frictionally oppose abnormal vibrations of the spindle, said frictional damping device including means for automatically returning said device to a predetermined normal position upon resumption of said normal vibrations, and means for operatively connecting said frictional dampening device with the bearing only when said radial deviations exceed a predetermined amount, said frictional dampening device includin an elastic ring concentric with the spindle axis, said connecting means including a flange movable radially with the bearing and operable, only when said last radial movement exceeds a predetermined amount, to compress the elastic ring radially.

NILS EDVIN SVENSJO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,816,325 Held July 28, 1931 1,887,315 Lindgren Nov. 8, 1932 2,025,787 Stahlecker Dec. 31, 1935 FOREIGN PATENTS Number Country Date 347,645 Germany Sept. 25, 1919 662,897 France Aug. 13, 1929 680,623 France May 2, 1930 

